STRUCTURE AND ROLE OF A TRANSFORMATION-SENSITIVE CELL SURFACE GLYCOPROTEIN

纤维连接蛋白是一种主要的细胞表面和细胞外基质。 参与细胞黏附和迁移的糖蛋白。合成的 从ITS序列衍生的多肽抑制剂被检测 对各种黏附系统的影响。五肽甘氨酸- 精氨酸-甘氨酸-天冬氨酸-丝氨酸(GRGDS)是最有效的抗肿瘤多肽 纤维连接蛋白介导的黏附，以及相关序列是活性的 用来代替维他林。这种多肽对层粘连蛋白几乎没有活性， 胶原蛋白，或细胞与细胞的粘连，表明特异性。一个 人工倒置肽鉴定出一种可能的常见 这五个系统中的四个系统中的函数分母。GRGDS 抑制小鼠B16黑色素瘤细胞实验性转移的研究 通过肺部定植和相关活动来衡量 的类似物与抑制细胞黏附的类似物非常接近 在试管中。多肽治疗也显著延长了患者的生存时间 这些动物。增加多肽的几种策略 体外和体内的有效性正在研究中。这 五肽黏附识别序列也似乎 果蝇原肠发育和脊椎动物体节的功能 体节前体细胞呈诱导细胞样细胞形成 粘附力。完全亲和力结合所需的额外区域 对细胞表面(50到100倍的增强)的定义 通过重组DNA表达研究。大纤维连接蛋白 在大肠杆菌中表达的lambda gt11融合蛋白片段 保持80%以上的黏附活性；真核细胞后 因此，不需要进行翻译修改。删除 诱变实验表明，第二个位点至少是 距离GRGDS站点20kD。另一类小说，细胞- 在其他地方发现了类型特定的结合位点 纤维连接蛋白位于受选择性剪接调控的部位。一种合成纤维 来自一个部位的多肽活性仅为完整多肽的2.4倍 纤维连接蛋白。关键氨基酸序列及其生物学意义 这些新区域在细胞迁移和转移中的作用 将会被确定。

Fibronectin is a major cell surface and extracellular matrix glycoprotein involved in cell adhesion and migration. Synthetic peptide inhibitors derived from its sequence were examined for effects on a variety of adhesion systems. The pentapeptide Gly- Arg-Gly-Asp-Ser (GRGDS) was the most effective peptide against fibronectin-mediated adhesion, and a related sequence was active for vitronectin. Such peptides had little activity on laminin, collagen, or cell-cell adhesion, indicating specificity. An artificial inverted peptide identified a possible common denominator of function in four of these five systems. GRGDS inhibited experimental metastasis of B16 melanoma cells in mice as measured by pulmonary colonization, and the relative activities of analogues closely matched those for inhibition of cell adhesion in vitro. Peptide treatment also substantially prolonged survival of these animals. Several strategies to increase peptide effectiveness in vitro and in vivo are under investigation. This pentapeptide adhesive recognition sequence also appears to function in Drosophila gastrulation and in vertebrate somite formation; somite precursor cells showed induced cell-cell adhesion. An additional region required for full-affinity binding to the cell surface (50- to 100-fold augmentation) is being defined by recombinant DNA expression studies. Large fibronectin fragments expressed in E. coli as lambda gt11 fusion proteins retained greater than 80% adhesive activity; eukaryotic post- translational modifications were thus not needed. Deletion mutagenesis experiments show that the second site is at least 20kD away from the GRGDS site. A separate class of novel, cell- type specific binding sites were discovered elsewhere in fibronectin at sites regulated by alternative splicing. A synthetic peptide from one site was only 2.4-fold less active than intact fibronectin. The critical amino acid sequences and the biological functions of these novel regions in cell migration and metastasis will be determined.